munch - munching squares screen hack

munch [-display host:display.screen] [-foreground color] [-background color] [-window] [-root] [-mono] [-install] [-visual visual] [-delay seconds] [-xor] [-noxor] [-shift] [-noshift] [-logminwidth minimum width]

The munch program performs the munching squares hack until killed. It picks square size, position, and gravity randomly; configurable options are listed below.

The munching squares hack consists of drawing Y = X XOR T for a range of X and T over and over until all the possible combinations of X and T have come up. It was reportedly discovered by Jackson Wright in 1962 and took 5 instructions of PDP-6 code.

munch accepts the following options:

-window

Draw on a newly-created window. This is the default.

-root

Draw on the root window.

-mono

If on a color display, pretend we're on a monochrome display.

-install

Install a private colormap for the window.

-visual visual

Specify which visual to use. Legal values are the name of a visual class, or the id number (decimal or hex) of a specific visual.

-delay seconds

How long to wait before starting over. Default 5 seconds.

-xor

Use the XOR drawing function. (Default.)

-no-xor

Don't use the XOR drawing function.

-shift

Start drawing the square at weird starting points. (Default.)

-no-shift

Don't shift and start drawing the square at weird starting points.

-logminwidth minimum-width

The logarithm (base 2) of the minimum with of a square (must be a power of 2, or some parts of the square aren't.)

DISPLAY

to get the default host and display number.

XENVIRONMENT

to get the name of a resource file that overrides the global resources stored in the RESOURCE_MANAGER property.

X(1), xscreensaver(1), http://www.inwap.com/pdp10/hbaker/hakmem/hakmem.html, http://www.comedia.com/Hot/jargon_3.0/JARGON_M/MUNCHSQR.HTML

Quoted from HAKMEM, for historical interest. As that document says, "Unless otherwise stated, all computer programs are in PDP-6/10 assembly language."

ITEM 146: MUNCHING SQUARES

Another simple display program. It is thought that this was discovered by Jackson Wright on the RLE PDP-1 circa 1962.

DATAI 2 ADDB 1,2 ROTC 2,-22 XOR 1,2 JRST .-4 2=X, 3=Y. Try things like 1001002 in data switches. This also does interesting things with operations other than XOR, and rotations other than -22. (Try IOR; AND; TSC; FADR; FDV(!); ROT -14, -9, -20, ...)

ITEM 147 (Schroeppel):

Munching squares is just views of the graph Y = X XOR T for consecutive values of T = time.

ITEM 148 (Cohen, Beeler):

A modification to munching squares which reveals them in frozen states through opening and closing curtains: insert FADR 2,1 before the XOR. Try data switches =

4000,,4 1000,,2002 2000,,4 0,,1002 (Notation: <left half>,,<right half>)

Also try the FADR after the XOR, switches = 1001,,1.

Copyright © 1997 by Tim Showalter. Permission to use, copy, modify, distribute, and sell this software and its documentation for any purpose is hereby granted without fee, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation. No representations are made about the suitability of this software for any purpose. It is provided "as is" without express or implied warranty.

Tim Showalter <tjs@andrew.cmu.edu>, 17-Jun-97, based on what's in the Jargon File and stealing stuff from existing xscreensaver modules.